Why are balance weights fitted to the crank webs of some engines and moment compensators on some engines

In the case of the 4-stroke medium speed engine , balance weights on crank webs restricted to half the total reciprocating mass is fitted to crank webs only for the odd number of cylinder in line engines. This reduces the resultant primary and secondary couple balance by about 50 percent.

In the case of the 2-stroke slow speed engine moment compensator are fitted to neutralise the primaryand/or secondary couple imbalance.